Cryogenic fluids, that is, fluids having a boiling point generally below −150° C. at atmospheric pressure, are used in a variety of industrial applications. One example is in the packaging of food, beverages and other products.
One part of liquid nitrogen (a cryogenic fluid) warms and expands into 700 parts of gaseous nitrogen at ambient temperature. Based on this characteristic, automated dosing equipment and systems have been developed that precisely dispense measured doses of liquid nitrogen into product containers prior to sealing. The trapped liquid nitrogen vaporizes and thus creates pressure within the container so as to add rigidity to the container. This allows for a use of a thinner container wall which reduces material costs and weight. Alternatively, for preservation and modified packaging (MAP) applications, the rapidly expanding gas is allowed to escape before the product packaging is sealed, flushing out oxygen and extending product life. In still another application, a dose of liquid nitrogen is introduced to “lock in” and surface freeze the food product (such as novelty ice cream).
A typical prior art dosing system is illustrated in FIG. 1. The liquid nitrogen is stored in a vacuum-insulated bulk tank 20 and transferred, via vacuum-insulated piping 22, to a phase separator 24. Liquid nitrogen is then provided via line 26 to a doser, indicated in general at 28. The doser includes a doser body 30 which houses an insulated cryogen source reservoir that receives the liquid nitrogen from line 26. A dosing arm 32 is connected to the doser body 30 and is in communication with the cryogen source reservoir. A dosing head 34 is positioned on the distal end of the dosing arm. The dosing arm 32 includes vacuum-insulated piping so that liquid nitrogen is supplied from the cryogen source reservoir of the doser body to the dosing head 34. A conveyer of a product packaging system passes below the dosing head. The dosing head includes a valve that dispenses or injects droplets including very precise amounts of liquid nitrogen into product containers as they pass below the dosing head on the conveyer.
Prior art dosers use a fixed dosing arm extending from the doser body. This requires a number of different doser models to accommodate user applications requiring various arm lengths. Furthermore, dosers with fixed dosing arms increase the difficulty and cost in developing custom built solutions for accommodating user needs.